The present invention relates to a vehicle rear body structure for preventing heat from influencing a rear bumper by an exhaust muffler disposed at a rear of a vehicle body.
An exhaust muffler is disposed under the floor at a rear part of the vehicle body so as to be oriented in a longitudinal direction. In this muffler, a rear end face of a main body of the muffler faces closely a rear end portion of the rear part of the vehicle body and a tailpipe for discharging exhaust gases is extended to the rear from the rear end face of the muffler.
Incidentally, a bumper is disposed at a lower rear end portion of the vehicle body, and in many cases synthetic resin bumpers are adopted from the viewpoint of improved impact absorption properties, formability, external appearance and the like. On the other hand, the rear end portion of the muffler main body which is heated faces closely the front of such a synthetic resin bumper, and therefore, there a risk exists that the bumper face may deform from heat effects resulting from the heated muffler so disposed.
To cope with the risk, countermeasures are conventionally taken thereagainst which are illustrated in FIGS. 3 and 4.
FIG. 3 is a longitudinally cross-sectional side view explaining a lower main portion of a rear part of the vehicle body which shows an example of the related art.
In the figure, reference numeral 51 denotes a rear cross member provided in a transverse direction of the vehicle body at the rear part thereof, and the rear cross member is provided to extend between rear end portions of left and right side members 52. A rear bumper 54 is disposed rearward of the rear cross member 51. A bumper face 54a of the rear bumper 54 confronts the rear cross member 51.
A muffler 53 is disposed below the rear cross member 51 in such a manner as to be oriented in a longitudinal direction of the body. An exhaust tailpipe 53c is provided to protrude to the rear from a rear end face 53b of a cylindrical main body 53a having a large diameter, and the rear end face 53b of the muffler 53 approaches a bottom piece portion 54b bent to the front from a lower end portion of the bumper face 54a of the rear bumper 54, whereby that portion of the rear bumper is easily subjected to heat deformation.
As a result, part of the bottom piece portion 54b of the rear bumper 54 is cut to the rear to provide a notched portion 55 so that the closely disposed muffler 53 and rear bumper 54 are spaced away from each other via the notched portion 55 so provided to thereby prevent the heat deformation of the rear bumper at that portion that would otherwise result from heat dissipated from the muffler 53.
With the countermeasures illustrated in FIG. 3, since the bottom piece portion 54b of the rear bumper 54 which is easily heat deformed is cut to provide the notched portion 55, there are caused problems that the structure is not preferable to the quality in external appearance and that since part of every bumper has to be cut, the cutting work is complicated and troublesome.
FIG. 4 is a longitudinally sectional side view of a lower main portion of a rear part of the body of a vehicle which illustrates another example of the related art.
In this countermeasures, a muffler 53 is covered with a heat shield 56, and the heat shield 56 comprises an upper plate portion 56a for covering at least from a rear portion to a rear-half portion of a main body 53a of the muffler and an end plate portion 56b which is bent from a rear end portion of the upper plate portion 56a to suspend downwardly therefrom for covering at least an upper-half portion of a rear end face 53b of the muffler 53.
The heat shield 56 prevents heat related effects on the portion of the rear bumper 54 which is easily heat deformed especially at the end plate portion 56b. 
With the countermeasures illustrated in FIG. 4, while several inconveniences are caused by the provision of the notched portion in the rear bumper shown in FIG. 3, the following inconveniences are also caused. Namely, since the heat shield is needed, the number of parts is increased. Since supporting members and a supporting structure are separately needed for the heat shield, the structure of the rear part of the body becomes complicated. As a result, the structure is disadvantageous from the cost and weight point of view. In addition, since the heat shield is provided above the muffler under the rear part of the body where the space is limited between the muffler and the body, the capacity of the muffler is reduced, this leading to a risk that the performance of the muffler is affected.
The invention was made to solve the problems. It is an object of the present invention to provide a vehicle rear body structure for ensuring the prevention of heat related effects of a muffler on a rear bumper without substantially modifying any of the original configuration and structure of the rear bumper by, for example, providing a notched portion and hence damaging the external appearance of the rear bumper and implementing the prevention with a simple structure while reinforcing a rear part of the vehicle body.
In an attempt to solve the problems, according to a first aspect of the invention, there is provided a vehicle rear body structure in which a muffler is disposed below a rear cross member disposed in a transverse direction at a lower portion of a rear part of a vehicle body. In the vehicle rear body structure, a lower end portion of the rear cross member is extended downwardly to reach substantially the same height as that of a lower end portion of a rear bumper face disposed rearward of the rear cross member.
According to the first aspect of the invention, the lower end portion of the rear cross member which is extended downwardly to substantially the same height as that of the lower end portion of the rear bumper face is interposed between the rear end portion (rear end face) of the muffler and the rear bumper to function as something like a heat shield, whereby the effects of heat radiating from the muffler on a part of the rear bumper, which easily heat deforms, is thereby to protect the rear bumper from the heat from the muffler.